Re:Sound could not overcome the language of the Copyright Act which seems quite clearly intended to prevent this very result.
The definition of "sound recording" is as follows:
“sound recording” means a recording, fixed inany material form, consisting of sounds, whetheror not of a performance of a work, but excludes any soundtrack of a cinematographicwork where it accompanies the cinematographic work;The Copyright Board had previously ruled that there was no basis under the Copyright Act to impose these tariffs.
Here's the Court's decision.
Here's the Board's decision.